A measuring device for measuring structures on wafers or on a substrate (mask for producing semiconductors) is disclosed in the lecture script “Pattern Placement Metrology for Mask Making” by Dr. Carola Bläsing. The lecture was given on the occasion of the Semicon conference, Education Program, in Geneva on Mar. 31, 1998. The description therein discloses a coordinate measuring device, the measuring method and the basic structure of the coordinate measuring device including accessories. The coordinate measuring device is arranged in a climatic chamber to provide the same climatic conditions with respect to temperature and humidity for the measurement within the climatic chamber.
German Patent DE 196 28 969 also discloses a coordinate measuring device including a two-beam interferometer for determining the position of a measurement table. The two-beam interferometer has an effectively reduced influence of the wavelength changes on the wavelength measurement. This is achieved by inserting a light-transmitting, closed, incompressible body into the optical reference path or the optical measurement path so that, with the movable measurement mirror in a particular position, the portions of the optical reference path and the optical measurement path located outside the body have the same length.
German published application DE 199 49 005 discloses a means and a method for introducing various transparent substrates into a high-precision measuring device. The high-precision measuring device and the additional elements for transporting the transparent substrates, which are associated with the high-precision measuring device, are arranged in a climatic chamber. The climatic chamber thus allows reducing the influence of pressure, humidity and temperature considering the ambient conditions. U.S. Pat. No. 5,469,269 particularly discusses the influence of fast, random air movements, such as they occur after opening or closing doors or after movements in the vicinity of the measuring device. The localized air pressure variations caused thereby result in local changes of the refractive index and thus wavelength changes in the light beam. It is suggested to solve the problem by casing the optical measurement and reference paths in tubes that are open at both ends. Air with a defined temperature stabilization or temperature-stabilized gas is to be blown into the tubes. Tubes with a telescope-like extension mechanism are provided for the optical measurement path, which is variable in length. By casing most of the light beam, the influence of fast air pressure variations is mostly prevented.